There are many factors which affect the amount of concentration that a driver may devote to the primary task of driving a vehicle. As the number of devices (such as car phones, navigation systems, infotainment systems) provided in vehicles continues to increase, the opportunity for a driver to become distracted from driving the vehicle also increases. Many reported automobile accidents involve some sort of driver distraction. Actions which are considered to be secondary tasks, such as pushing a button or adjusting a knob (eg. tuning a radio or adjusting the heating controls) often require the driver to glance away from the road ahead in order to locate the button or knob. While the driver is glancing away from the road ahead to perform this secondary task, the driver's attention to the primary task of driving the vehicle is distracted and thus secondary tasks are associated with an increased level of risk. Because of the increased risk associated with driver distraction, it is desirable to provide a system that utilises a measure of driver distraction which is derived from the driver's manipulation of controls, in order to adjust various parameters of the vehicle to account for the drivers lack of attention to driving.
US-A-20030149545 discloses a method for calculating an indicator of driver distraction during performance of a task by the driver based on a correlation of the type and elapsed time of the task with other information in order to facilitate a threat assessment decision.
GB-A-2485027 discloses a method which can be employed for lowering the threshold for issuing a warning message when it is detected that the driver is activating a control such as a seat adjuster.
US-A-20040073367 discloses a method for alerting the driver of a vehicle of a potential collision with a detected object by calculating a predicted acceleration of the vehicle and taking into account whether the driver is activating the vehicle's radio or heating system.
Performing a secondary task whilst driving is only one of several factors which can affect a risk level. For example, environmental factors such as whether it is dark or not and whether it is raining will also have an influence. If the driver has been driving for a long time and therefore may be tired, or if the cabin conditions are uncomfortable in any way then factors such as these may also contribute to the risk level. The primary task of driving the vehicle also has its own associated risk level. A high workload such as frequent changes in steering angle, gear changing or braking can be associated with a higher risk level than cruising at a constant speed with little or no change in direction.
Information on the aforementioned factors and other factors of a similar nature which may have some bearing on the drivers ability to maintain concentration or which may affect the safety of the vehicle and its occupants, may be gathered by the various on-board systems and sensors which are fitted to a vehicle. For example the various control management systems in the vehicle can readily monitor steering angle deflection, braking effort and vehicle speed. Sensors on the vehicle can detect if it is raining and the ambient light level. Navigation systems can monitor distance travelled and journey time. A radio or heating control can record when it is being adjusted. A head position sensor can monitor head movements of the driver to indicate if his/her eyes have been taken off the road for any length of time. Information relating to such factors which affect level of risk will be referred to hereafter as “distraction indicators.” It would be advantageous to provide filtering of all these distraction indicators in order to arrive at an estimation of a risk level which may be utilised by an on-board safety system such as a collision avoidance system for example.